Since the inception of the electric guitar, guitarists have created overtones by overdriving amplifiers, and many guitarists use these overtones as a stylized element of their music. In particular, many musicians deliberately turn up a vacuum tube amplifier to the point where distortion (e.g., clipping) is clearly audible in the output signal. This distortion may range from a slight added “edge” with some increase in sustain, up to a thick fuzzy sound whose tonality is almost unrecognizable as that of the input signal. Although the overdriving of amplifiers is predominantly used with an electric guitar, some have also used it with the bass guitar or even a keyboard.
These artists, however, face the dilemma of either being able to preserve these overtones in their music or being able to adjust the volume of the output amplifier to lower levels where the overtones are not produced. Guitarists, for example, often times must sacrifice these desired overtones because the volume at which their amplifiers produce these overtones in simply too loud for small clubs, recording studios, townhouses or apartments.
Many circuit designs and additional components have been created in an attempt to simulate the overtones that occur when an amplifier is overdriven without actually overdriving the amplifier. For example, commercial devices have been developed and sold that either change or add circuitry in the path which the audio signal travels. More specifically, devices have been developed that generate signals that attempt to replicate the overtones that are created when an amplifier is overdriven. These replications, however, typically do not provide the same quality of overtones that are naturally produced by an overdriven amplifier.
Alternatively, many modern guitar amplifiers have a preamplifier stage, which can be made to distort heavily and the final output volume can be controlled by changing the gain on the later stage(s) of amplification. This approach, however, only introduces class A-type distortion from the preamplifier and does not enable the distortions created by an overdriven output stage, which many artists are most interested in, to be introduced into the audio signal.
Moreover, even when a tube amplifier is not overdriven, there are inherent distortions created when a tube amplifier drives a transducer, and many musicians desire to maintain these distortions as well. Accordingly, a method and an apparatus are needed to overcome the shortfalls of present technology.